use memmem and strndup from FreeBSD on Darwin (Thanks Marcus)

include/util.h

@@ -164,4 +164,18 @@ char *get_process_filename(const char *prefix);
  */
 void i3_restart(bool forget_layout);
 
+#if defined(__OpenBSD__) || defined(__APPLE__)
+
+/*
+ * Taken from FreeBSD
+ * Find the first occurrence of the byte string s in byte string l.
+ *
+ */
+void *memmem(const void *l, size_t l_len, const void *s, size_t s_len);
+
+#endif
+
+#if defined(__APPLE__)
+#endif
+
 #endif

src/util.c

@@ -448,9 +448,7 @@ void i3_restart(bool forget_layout) {
     /* not reached */
 }
 
-#if 0
-
-#if defined(__OpenBSD__)
+#if defined(__OpenBSD__) || defined(__APPLE__)
 
 /*
  * Taken from FreeBSD
@@ -485,4 +483,27 @@ void *memmem(const void *l, size_t l_len, const void *s, size_t s_len) {
 }
 
 #endif
+
+#if defined(__APPLE__)
+
+/*
+ * Taken from FreeBSD
+ * Returns a pointer to a new string which is a duplicate of the
+ * string, but only copies at most n characters.
+ *
+ */
+char *strndup(const char *str, size_t n) {
+    size_t len;
+    char *copy;
+
+    for (len = 0; len < n && str[len]; len++)
+        continue;
+
+    if ((copy = malloc(len + 1)) == NULL)
+        return (NULL);
+    memcpy(copy, str, len);
+    copy[len] = '\0';
+    return (copy);
+}
+
 #endif